DAB+ Digital Radio RF Transmission Planning

ASBU / WorldDAB - DAB+ Workshop, Amman, Jordan 23-24 August 2017

DAB+ Digital Radio RF Transmission Planning

Dr Les Sabel, WorldDAB Technical Committee

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• Planning levels – mainly ITU / EBU but each country has its own slight

variations

• SFN operation

- Why is this good/useful

- Efficiency of DAB (relative to FM)

• Interference issues

- coordination

• Design process

• Coverage examples

RF Planning

2

Capacity and coverage requirements

RF Coverage – Requirements

How many services (now and later)

• Defines how much spectrum is needed

• E.g. Sydney uses 3 ensembles (5.136MHz) for approx 63 services

Number of services in each Region or Licence Area?

Service capacity includes both audio and PAD

How much of the population must be covered

• Define minimum coverage requirements

• Significant for difficult terrain and large areas

• Increases to (near) 100% of the country as the deployment process approaches

Analogue Switch Off (ASO)

3

Spectrum Requirements

RF Coverage – Requirements

What VHF band III capacity is available?

• Which channels?

Multiple Frequency Network planning – cellular design

• Power levels are critical

• Coverage vs Co-Channel Interference (CCI)

• Adjacent Channel Interference (ACI) with other/adjacent cells / LAPs

• spectrum reuse

• typical cellular design requires >4 times single cell capacity dependant on

terrain and coverage requirements

4

2 DTV channels allocated

14MHz = 8 DAB channels = 8A, B, C, D, 9A, B, C, D

Transmission – Frequency plan

UK channel allotments

Australian

Band III

allocation

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Transmission – Frequency plan

Germany

Full VHF Band III

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Overview Signal bandwidth = 1536 carriers at 1kHz each => 1.535MHz

Channel bandwidth = 1.712 MHz

Channel edge

shoulders at -40dB

Far off adjacent

power at <-60dB

RF spectrum

Transmission

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Transmission channels

- Line of Sight / Ricean

- Rayleigh

Transmission

The received signal is

composed of multiple signal

paths and USUALLY has no

direct line of sight

component, i.e. is a

Rayleigh channel

The received signal is

composed of multiple signal

paths and USUALLY has no

direct line of sight component,

i.e. is a Rayleigh channel

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Australian Commercial Radio Planning targets (2017)

RF Coverage – Levels

Below 50dBuV/m is considered to provide unreliable coverage in vehicles

Some areas may receive marginal coverage but patchy coverage is unsatisfactory

> 60 dBuV/m

54 – 60 dBuV/m

50 – 54 dBuV/m

Defined by ITU / EBU but each country has its own slight variations

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Planning Considerations

RF Planning – Tools, Methods and Standards

ITU

• BS.1660 -includes guidelines for planning but is now quite old

EBU

• Recommendation R 138 - DIGITAL RADIO DISTRIBUTION IN EUROPE

• Recommendation 2: Immediate deployment be done using DAB transmission

as defined in ETSI EN 300 401 with DAB+ services as defined in ETSI TS 102

563 for digital radio broadcasting in VHF Band III;

• TR 021 - TECHNICAL BASES FOR T-DAB SERVICES NETWORK PLANNING

AND COMPATIBILITY WITH EXISTING BROADCASTING SERVICES

• Frequencies and protection

• TR 025 - REPORT ON FREQUENCY AND NETWORK PLANNING

PARAMETERS RELATED TO DAB+

• Receiver C/N values

• BPN003 - TECHNICAL BASES FOR T-DAB SERVICES NETWORK PLANNING

AND COMPATIBILITY WITH EXISTING BROADCASTING SERVICES

• Transmission planning levels, receiver C/N and SFN operation and gain

Be cautious

Theory does not always = practice!

Propagation modelling should

always be followed up with in field

measurements to tune models to

obtain the most accrate results

Science is improving predictions

and planning process

EBU Broadcast Network Planning

group is reworking the EBU DAB+

planning guidelines given recent

measurements and results

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Multi-Frequency Networks and Single Frequency Networks

RF Planning - Network Types

• Single frequency network.

• Multiple transmitters

• Can be any combination of high, medium and

low power transmitters

MFN

e.g. Main Tx and 2 Gap Fillers SFN

e.g. Main Tx and 2 Gap Fillers

SFNs are a more efficient

use of spectrum

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RF Network Options


Covering a specific area

e.g. A Licence Area

DAB: 7 transmitters on one frequency

FM: 7 transmitters on 7 frequencies

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SFN coverage in Sale, Victoria, Australia

SFN example

7 transmitters to cover 200km ranging from 1 to 5kW each

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Link Fed Repeaters


The repeater is fed an ETI/EDI signal via a link

- Microwave

- Telco landline (fibre, dedicated or shared, diversity)

Telco Link

Microwave link

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On Channel Repeater


Receives the signal off-air and then retransmits on the same frequency

Echo cancelling techniques allow repeaters to be built which can re-transmit on the

same frequency

For FM the repeater

must translate the

received signal to

another frequency

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Licence areas - Northern NSW example

RF Planning – Multi-Frequency Network

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Interference between Sweden and Germany and Denmark

Cross border coordination

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Interference Considerations


ACMA defined Protection Ratios

Unwanted

Wanted CCI Protection Ratio =12dB

ACI Protection Ratio = -40dB

Affects the re-use distance in

multi-frequency networks

Higher value results in more

conservative planning

Affects the allowed impact on adjacent

channel transmissions in multi-frequency

networks

More negative value provides less protection

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Local transmission punching a coverage hole into a wide area transmission

ACI coverage hole punching

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The Design Cycle

RF Planning – Levels, methods and standards

• The first loop is the hardest

• A test transmission will provide

the best learning experience

• Use the initial system results

to help design future systems

Requirements

Model

Design Build

Verify

adjust

test

formalise

adjust

science

details

publish

Engineering collaboration helps

minimise the system design and

deployment effort and

maximises benefits to listeners

and in turn broadcaster returns

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The Design Cycle – Coverage Modelling

RF Planning – Levels, methods and standards

• Model coverage then interference

• Main high power site first, then in-fills/repeaters

• Use antenna pattern HRP and down tilt VRP (if required)

• Tuning the coverage model to maximise accuracy

– Cartography resolution

– propagation model

– clutter parameters

• Test transmissions at lower power will allow more accurate design through empirical

verification in the field

– At least for initial sites

– Is terrain / clutter dependant

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The Design Cycle


• A cooperative and collaborative process between both

broadcasters and the regulator

• Site selection

– High sites will provide the best coverage but also the longest

distances for CCI

– Use the same sites for multiple ensembles if possible

– National and commercial coverage variations

– Collocate with VHF TV to minimise ACI issues

• Antenna selection

– Patterns, Down tilt, Gain

• higher gain = lower power costs but more initial Capex

• Antenna patterns may need to be shaped to minimise interference

– DC grounded antennas

Save Money / Make Money

22

High Power High Tower v Low Power Low Tower selections

• Higher sites will always provide greater coverage due to increased line-of-sight areas

• Terrain is the largest impact on coverage area, large buildings are equivalent to hills!

• Uneven and shadowed terrain requires increased main site power and/or increased

repeaters

RF Planning - Transmission network design considerations

Type Power

(kW ERP)

Height above

served area (m)

Best use

HPHT 20-50+ >250 wide area coverage but may experience

shadowed areas especially in the distant

coverage areas

Typical coverage radius = 30 – 80km

MPMT 5-20 50-250 undulating areas with no high transmission site


LPLT 0.3-5 <50 local area coverage


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Terrain

shielding

and

undulations

Sydney

northern

beaches


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City building shielding - Melbourne


Mt Dandenong

transmitter 45kms

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HPHT – LPLT Cost implications

• HPHT will usually give best coverage kms2/$

• City sites can be very expensive, even for LPLT

• High population density drives prices up even for sites like water towers

• Telco towers are often too low!

• Site costs are often the largest component of Opex for main AND repeaters

• Site selection for cost optimisation is time consuming – especially for multiple

repeater sites in large cities

• The number of main HPHT sites in large cities are often limited


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Allotment planning process

Iterate the loop until the

population coverage and CCI

requirements are met

Define transmitter sites and

parameters

Model population coverage

Model CCI

Select area frequency channel to

minimise CCI

Review

Requirements

Local / regional /

national areas

Identify population

coverage areas

Sometime cost minimisation

will require trade-offs in

coverage and/or interference

targets

ACI and self-interference will

also need to be examined

As sites are built the coverage

can be measured and the

models adjusted to maximise

accuracy as the roll-out

progresses

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Licence areas – South Eastern Australia example

RF Planning – Multi-Frequency Network

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Frequency Planning

• Cultural considerations - may need to deliver the same/equivalent content in different

languages for different areas

• Ensembles with ANY different content will need to use different ensemble frequencies

in an MFN configuration within CCI rules

• The terrain of each area may provide natural boundaries to facilitate more efficient

frequency re-use

• Existing use of the VHF Band III spectrum must be taken into account to ensure that

interference is within defined limits


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Adelaide Licence Area

RF Planning - Design examples

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Adelaide terrain viewed from the south


Mt Lofty transmitter

site Adelaide CBD

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Adelaide TV Towers at Mt Lofty


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Adelaide TV Towers at Mt Lofty


80kms

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Brisbane Licence Area


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Brisbane EMAX vs. ERP


1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

180

0

270 90

E / Emax

BRISBANE ACMA DRCP 18 Dec 08

RF network

design must

consider

interference and

well as coverage

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Brisbane

Licence Area

23kW ERP


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Brisbane

Licence Area

Drive test

results


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Ipswich


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Proposed high power option

50kW ERP


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Brisbane

Licence Area

50kW ERP

Notch removed


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Brisbane

Licence Area

23kW

With notch


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Sydney Licence Area


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Sydney Terrain viewed from the East


Artarmon transmitter site

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Sydney Terrain – looking north over Camden valley


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Sydney LAP

RF Planning - OCR Case Study

Single 50kW Tx

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Sydney LAP


Single 50kW tx

50 km

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Sydney LAP


Single 50kW tx

52 km

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Sydney LAP


Single 50kW tx

6 repeaters

No network

gain shown

52 km

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Artarmon main

Tx only

50kW

200m AGL

Areas of

shadowing

shown

Prediction is

optimistic due

to clutter

generalisation


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Centrepoint

only

300W

125m AGL


50

Redfern only

300W

50m AGL


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All


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Sydney city centre


Impulse response for an

in-building receiver in

Surry Hills – 5th floor

Main Tx at Artarmon

Centrepoint repeater

Redfern repeater

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Artarmon to Centrepoint = 7.68km

Centrepoint to Office = 1.6km

Total = 9.28km = 30.9uS

Artarmon to Redfern = 9.76km

Redfern to office = 1.40 km

Total = 11.16km = 37.2uS

Artarmon to office = 9.27km

Path difference of 10m=0.03uS

OCR processing delay=27uS

Path diff = 1.88 = 6.3uS

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Sydney city centre repeaters


Ch 9B

27uS 6.9uS = 180m error

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Sydney city centre repeaters


Ch 9C

27uS 6.9uS

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Summary – Top Tips

RF Planning - RF planning

1. Know what you want to achieve – the BIG PICTURE

2. Be Collaborative in Engineering the system – Competitive on Content

3. Work with your Regulator to ensure that all parties are considered

4. A successful rollout will require consultation with retailers, automotive etc

5. Use the design cycle to your advantage – process is important

6. RF Coverage modelling is essential

7. Beware of Co-Channel Interference and Adjacent Channel Interference

8. Plan field testing and tune your models – coverage and interference

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Thank you

For further information, please contact:

www.worlddab.org

or

[email protected]

http://www.worlddab.org/

DAB+ Digital Radio RF Transmission Planning

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